This invention has relation to equipment useful to transport elongated bundles, such as banded lumber and similarly stacked unbanded lumber, and the like, to and from positions of storage or use. Typically, fork lift trucks are used for such a purpose, but, before the present invention, these trucks have to be turned and positioned in transverse relationship to the elongated bundle or lumber stack, for example. The fork lift truck tines are then raised by the lift truck prime mover and the lifted bundle then backed up far enough away from any adjacent bundles or walls so that the truck can back around to a position at 90.degree. from its pick-up position in order to transport the load transversely of the truck to its new location for storage or use. Obviously, the width of the pathway left open for such transportation must be substantially larger than the length of the bundle being transported.
When the bundle reaches its near new location, the fork lift truck must again be turned at 90.degree. to the longitudinal axis of the final resting place of the bundle, the truck and bundle must then be moved up close to any adjacent bundle, and the fork lift truck tines lowered to deposit the bundle on the ground or on bolsters to support it off of the ground.
In supporting such elongated bundles in a yard for storage or in a building for any purpose, in accordance with the prior art, sufficient space must be left between the last elongated bundle deposited and the edge of the yard or the wall of the building behind the truck to allow the fork lift truck room to pull its fork lift truck tines back out from under the bundle, and then to back around at 90.degree. with respect to the bundle discharge position so that the truck can go on to do other work.
Obviously if elongated loads could have been handled by a fork lift truck while the bundles or other loads were in longitudinal alignment with the longitudinal axis of the truck, the work path or pattern of the fork lift truck vehicle would be greatly reduced; bundles could be transported down narrow passages between lumber stacks, and increased storage density and superior stackability could be obtained. The fork lift truck could move to the end of the elongated bundle, pick up the bundle, carry it to the new location for use, put it down again, and back straight away from it.
Something somewhat similar has been quite recently tried and has apparently found some degree of success. An expensive single purpose load handling machine embodying a prime mover or truck with a hydraulically operable extensible load handling knuckle boom thereon is equipped with a rotating lumber grapple attachment at the outer end of the boom. This attachment embodies two support legs having rotatable tines at the bottom thereof, the support legs being designed to be placed by the knuckle boom adjacent the outer longitudinal edge of the bundle to be lifted, and the tines being adapted to be rotated to take position underneath of the bundle. The hydraulically extensible boom is then elevated to raise the bundle, and the knuckle boom is utilized, after the boom is extended, to rotate the elongated bundle on a central vertical axis should this be desirable.
The difficulty with this structure from a practical viewpoint is that the entire large expensive rig must be committed, at least temporarily, to one purpose operation, and the prime mover and the hydraulically operated extensible and elevatable boom cannot be used for other work whenever they are being used to transport elongated bundles longitudinally in line with the prime mover. Changeover from this mode of operation to use in some other manner entails a large changeover or "down" time period. This takes the structure out of the economic reach of the small and medium size operator who needs and uses a fork lift truck for many purposes but has need for moving elongated bundles longitudinally from time to time and on short notice.
Experimentation has been going along with the hydraulic knuckle boom structure as set out above, but it is not known by the present inventor as to whether his invention came before or after the development of it.
Efforts have been made to adapt conventional fork lift truck structures to the handling of elongated bundles in longitudinal alignment with the fork lift truck bodies. See for example U.S. Pat. No. 2,950,830 to Johnson, granted Aug. 30, 1960 and U.S. Pat. No. 2,724,521 to Squires, granted Nov. 22, 1955. Both of these patents try to solve the problem by supporting the elongated bundle or other load in cantilever fashion from one end of the load. Obvious limitations of these structures are the structural strength of the load being lifted, and the movement of the center of gravity of the truck and the load forward as the weight of the load is increased and as the length of the load is increased. Further, the cantilever aspect of the load resting at the end of the tines in downward direction and being forced against the structure above the tines in the upward direction exerts very large and destructive torques on the mechanisms.
Another attempt to use the basic fork lift truck structure to handle enlongated bundles in longitudinal alignment with the truck axis is shown in U.S. Pat. No. 3,984,019 to Brudi, granted Oct. 5, 1976. This is another special purpose attachment which must be connected and disconnected from the front of the fork lift truck with some difficulty and considerable "down" time. Further, this structure relies on a horizontally extending boom which comprises a parallelogram linkage which swings horizontally from side to side to carry a pair of parallel and constantly aligned tines transversely alternately under and out from under a load to be lifted. This structure has the obvious disadvantage of needing the full clearance of the width of the bundle on the working side of the bundle, or it could not be lowered down next to the bundle in the first place and could not be moved clear of the bundle and raised away from it when the bundle reaches its final resting point.
A search was made preparatory to writing this patent application, and the only patents located are the three listed above.